Hybrid utility vehicle

ABSTRACT

A vehicle comprises a transaxle, a battery and a load carrying bed. The transaxle includes a casing incorporating a drive train and supporting an axle and includes an electric motor mounted on the casing to drive the axle via the drive train. The battery is provided for supplying electric power to the electric motor. The transaxle and the battery are disposed below the load carrying bed so as to overlap the load carrying bed when viewed in plan.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/660,650, filed on Jul. 26, 2017, which is a continuation of U.S.application Ser. No. 14/668,440, filed Mar. 25, 2015, which is acontinuation of U.S. application Ser. No. 13/623,663, filed Sep. 20,2012, which claims the benefit of U.S. Application No. 61/538,641, filedSep. 23, 2011, which benefit is also claimed by this application. Theseapplications are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a vehicle, such as a utility vehicle,equipped with an electric transaxle integrated with an axle and anelectric motor for driving the axle. Also, the present invention relatesto a transmission assembly adapted to be driven by an engine andprovided with an electric motor for assisting the engine. Especially,the transmission assembly includes a continuously variable belttransmission (CVT).

Background Art

As disclosed by U.S. Pat. No. 7,926,387 B, a conventional utilityvehicle is equipped with a rear transaxle under a load carrying bed. Therear transaxle includes a housing incorporating a gear train and adifferential. An engine and a hydrostatic stepless transmission (HST)are directly mounted on the housing. The rear transaxle supports rearwheel axles. A front transaxle supporting front wheel axles is separatedfrom the rear transaxle and is disposed at a front portion of thevehicle forward of the load carrying bed. A housing of the fronttransaxle incorporates a differential, and a PTO shaft projects from thehousing of the rear transaxle so as to be drivingly connected to thedifferential of the front transaxle via a propeller shaft. Power of theengine is transmitted to the rear wheel axles and the front wheel axlesvia the HST and the gear train.

As disclosed by U.S. Pat. No. 7,946,953 B and US 2010/0263958 A, anotherconventional engine utility vehicle is equipped with a mid-shippedengine, a rear transaxle casing supporting right and left rear wheels, afront transaxle casing supporting right and left front wheels, and atransmission for distributing power of the engine between the front andrear transaxle casings. Each of the front and rear transaxle casingsincorporates a differential unit differentially connecting the right andleft front or rear wheels to each other. The transmission is acombination of a hydrostatic stepless transmission (HST) and a geartransmission, or a combination of a belt transmission serving as acontinuously variable transmission (CVT) and a gear transmission, forexample.

Some types of sports utility vehicle are mainly used for huntingpurposes. Silence is a matter of great importance for hunting vehicles.Therefore, many utility vehicles used for hunting are electric vehiclesequipped with electric motors. However, hunting vehicles are sometimesdesired to have great power, such as engine power, for high-speedtraveling on roads, for high-torque traveling on rough fields, or forother purposes. Further, recently, people dwelling in residentialdistricts have greatly demanded utility vehicles because the utilityvehicles are convenient for various daily living tasks, e.g., for takingchildren to and from school or kindergarten bus stops. The residentsdesire silence, compactness and economy of the utility vehicles. Anelectric motor is an effective means for achieving the silence. However,the residents also sometimes desire the utility vehicles to have greatpower, such as engine power, for high-speed traveling on roads or otherpurposes.

To satisfy the above-mentioned desires, a utility vehicle is expected tohave an engine and an electric motor and to be configured so thateither/both electric power or/and engine power can be optionallyselected as power for driving the utility vehicle, while ensuringcompactness in structure and economy in structure and in powerconsumption.

Further, as disclosed by US 2010/0120565 A, there is a well-knownconventional vehicle equipped with a transmission assembly that includesa belt transmission driven by an engine, and a gear transmission drivenby the belt transmission. This belt transmission is a continuouslyvariable transmission (CVT) that automatically changes its speed ratioin correspondence to an output speed of the engine and an actualtraveling speed of the vehicle. The defect of the CVT is a delay ofreduction of output speed. In other words, a vehicle equipped with amulti-speed gear transmission can greatly reduce the traveling speed bya speed-down shift operation of the gear transmission. Such an efficientreduction of traveling speed is called “engine brake”, however, the CVTcannot serve as the engine brake in at least a part of its overall speedshift range. As a result, the CVT needs to apply a mechanical brake toefficiently reduce a traveling speed of a vehicle in such a case wherethe vehicle descends a slope.

BRIEF SUMMARY OF THE INVENTION

A first object of the invention is to provide a vehicle that isadaptable as a compact and economical utility vehicle which can travelsilently by use of electric power. Preferably, the vehicle is configuredso that either electric power or engine power can be optionally selectedfor driving the vehicle.

To achieve the first object, a vehicle according to the inventioncomprises a transaxle, a battery, a load carrying bed and a seat. Thetransaxle includes a casing incorporating a drive train and supportingan axle and includes an electric motor mounted on the casing to drivethe axle via the drive train. The battery is provided for supplyingelectric power to the electric motor. The transaxle is disposed belowthe load carrying bed so as to overlap the load carrying bed when viewedin plan. The battery is disposed below the load carrying bed or the seatso as to overlap the load carrying bed or the seat when viewed in plan.

Therefore, the vehicle can travel silently by the electric power of theelectric motor. The vehicle is advantageous in expanding an availablespace, such as an operator's space involving the seat forward (orrearward) of the load carrying bed, while ensuring compactness of theentire vehicle because a dead space below the load carrying bed isutilized for arranging the transaxle including the electric motor andbecause the dead space below the load carrying bed or a dead space belowthe seat is utilized for arranging the battery. Further, the battery canbe exchanged for a new battery easily by moving the load carrying bed orthe seat for opening the space below the load carrying bed or the seat,thereby improving maintenanceability of the battery.

Preferably, in a first aspect of the vehicle, the transaxle isconfigured so that the electric motor and a portion of the casingsupporting the axle are extended from another portion of the casingincorporating the drive train so as to vertically offset from each otherand so as to overlap each other when viewed in plan.

Therefore, the electric motor and the portion of the casing supportingthe axle can be extended horizontally from the portion of the casingincorporating the drive train so as to vertically minimize thetransaxle, while the vertical offset of the electric motor and theportion of the casing supporting the axle, which overlap each other whenviewed in plan, minimizes the transaxle horizontally (laterally orlongitudinally), thereby further enabling the transaxle to be compactlydisposed below the load carrying bed so as to further ensure thecompactness of the entire vehicle and so as to further expand anavailable space in the vehicle such as the operator's space. Further,the electric motor can be easily attached or detached to and from thecasing of the transaxle (preferably, the portion of the casingincorporating the drive train) at a position where there is no fear ofinterference with the portion of the casing supporting the axle, therebyimproving the maintenanceability of the electric motor, and whereby thevehicle can be designed to have the electric motor attached optionally.For example, the electric motor is extended rearward from an upperportion of the portion of the casing incorporating the drive train andabove the portion of the casing supporting the axle. In this case, thevehicle may be configured so that a vehicle frame under the loadcarrying bed has a rear end portion which can open and shut for easilyattaching or detaching the electric motor to and from the casing.

Preferably, in a second aspect of the vehicle, the transaxle is definedas a first transaxle, and the vehicle further comprises a secondtransaxle supporting another axle.

Preferably, in the second aspect, an end of the battery toward thesecond transaxle is closer to the first transaxle than the secondtransaxle.

Therefore, a distance of the second transaxle from the battery is longerthan another distance of the first transaxle from the battery so thatthis longer distance of the second transaxle from the battery can beused to ensure the sufficiently large operator's space.

Preferably, in the second aspect, the second transaxle is drivinglyconnected to the first transaxle so that power of the electric motor istransmitted to the second transaxle.

Therefore, the electric motor of the first transaxle also serves as apower source for the second transaxle, thereby reducing the number ofmembers serving as power sources so as to reduce costs and so as toexpand a free space in the vehicle or so as to minimize the vehicle.

Preferably, in the second aspect, the second transaxle includes a secondelectric motor for the axle of the second transaxle, and the batteryalso supplies electric power to the second electric motor.

Therefore, the vehicle needs no element for drivingly connecting thesecond transaxle to the first transaxle or a power source that isdistant from the second transaxle, thereby expanding a free space suchas an operator's space or minimizing the vehicle.

Further preferably, a pair of transaxles which are identical to eachother serve as the first and second transaxles.

Therefore, the transaxles are standardized so as to reduce costs formanufacturing the vehicle.

Further preferably, each of the pair of transaxles serving as the firstand second transaxles is configured so that the electric motor and aportion of the casing supporting the axle are extended from anotherportion incorporating the drive train so as to vertically offset fromeach other and so as to overlap each other when viewed in plan.

Therefore, in addition to the economical standardization of thetransaxles, the second transaxle is also subjected to theabove-mentioned advantageous compactness of the first transaxle.

Preferably, in a third aspect of the vehicle, the vehicle furthercomprises an engine for driving the drive train. The engine is disposedbelow the load carrying bed or the seat so as to overlap the loadcarrying bed or the seat when viewed in plan.

Therefore, the vehicle is adaptable as a hybrid vehicle equipped withthe engine and the transaxle including the electric motor. Further, thedead space below the load carrying bed or the seat is utilized forarranging the engine, thereby expanding an available space in thevehicle, such as the operator's space involving the seat forward (orrearward) of the load carrying bed, while ensuring compactness of theentire vehicle.

Preferably, in the third aspect, the vehicle further comprises atransmission casing incorporating a transmission mechanism fortransmitting power from the engine to the axle of the transaxle.

Therefore, the vehicle is adaptable as a hybrid vehicle that can drivethe axle by the engine and/or the electric motor of the transaxle.

Further preferably, the transmission casing is disposed below the loadcarrying bed or the seat so as to overlap the load carrying bed or theseat when viewed in plan.

Therefore, the dead space below the load carrying bed or the seat isutilized for arranging the transmission casing, thereby expanding anavailable space in the vehicle such as the operator's space whileensuring compactness of the entire vehicle.

Preferably, the vehicle further comprises a second transaxle supportinganother axle. The transmission mechanism in the transmission casing alsotransmits power from the engine to the second transaxle.

Therefore, power of the engine is distributed between the axles of thetwo transaxles via the transmission mechanism in the transmissioncasing. The electric motor can assist the engine for driving the axle orcan drive the axle while the axles receive no power from the engine.

Preferably, in the third aspect, the transaxle is configured so that theelectric motor and a portion of the casing supporting the axle areextended from another portion of the casing incorporating the drivetrain so as to vertically offset from each other and so as to overlapeach other when viewed in plan.

Therefore, the compactness of the transaxle due to the verticaloffsetting of the electric motor and the portion of the casingsupporting the axle overlapping when viewed in plan is furtheradvantageous for the vehicle equipped with the engine (and thetransmission casing) in expanding an available space in the vehicle suchas the operator's space while ensuring the compactness of the entirevehicle.

To achieve the first object, an alternative vehicle according to theinvention comprises right and left electric transaxles, right and leftfirst drive wheels, an engine, right and left second drive wheels, atransmission for transmitting power from the engine to the right andleft second drive wheels, a generator, a battery, and a mode selectionmeans. Each of the right and left electric transaxles includes a casingincorporating a drive train and supporting an axle, and includes anelectric motor mounted on the casing to drive the axle via the drivetrain. The right and left first drive wheels are provided on the axlesof the respective right and left electric transaxles. The generatorgenerates electric power by driving the engine. The battery reserves theelectric power generated by the generator so as to supply the electricpower to the electric motors of the right and left electric transaxles.The mode selection means is provided for selecting either a first drivemode where only the right and left first drive wheels are driven by theelectric motors of the respective right and left electric transaxles ora second drive mode where only the right and left second drive wheelsare driven by the engine via the transmission.

Therefore, an operator who operates the vehicle can operate the modeselection means so as to optionally select either the first drive modefor driving the vehicle by only electric power, thereby obtainingsilence, or the second drive mode for driving the vehicle by only enginepower, thereby obtaining high torque for efficient traveling of thevehicle. Such an optional selection of drive mode is advantageous inachieving an operator's desired traveling performance of the vehicle aswell as or rather than economizing power consumption of the vehicle.Further, the vehicle has neither means for transmitting power of theengine to the first drive wheels nor means for transmitting power of theelectric motors to the second drive wheels, thereby being simplified andeconomized in structure.

A second object of the invention is to provide a transmission assemblyincluding a belt transmission (CVT) driven by an engine and a secondtransmission driven by the CVT so that the transmission assembly canefficiently reduce its output speed in spite of the gradual speed-shiftof the CVT.

To achieve the second object, a transmission assembly includes a belttransmission, a second transmission, a housing and a motor generator.The belt transmission is driven by an engine. The second transmissionincludes a plurality of shafts including at least an input shaft and anoutput shaft. The input shaft is driven by the belt transmission, andthe output shaft is driven by the input shaft. The housing incorporatesthe second transmission. The belt transmission is attached to one sideof the housing. The motor generator includes a rotor and a stator. Themotor generator is mounted on another side of the housing opposite tothe belt transmission so as to function as either an electric motor fordriving the output shaft or a generator driven by the engine via thebelt transmission so that the motor generator serves as a regenerationbrake for braking the output shaft when the motor generator functions asthe generator. One of the plurality of shafts of the second transmissionis extended to serve as a rotor shaft provided thereon with the rotor.

Therefore, a vehicle equipped with an engine and the transmissionassembly can save the engine power consumption with the assistance ofthe motor generator functioning as the electric motor, and canefficiently reduce its traveling speed by the regeneration brakefunction of the motor generator functioning as the generator in such acase where the vehicle descends a slope. The transmission assembly canbe easily and compactly provided with the motor generator by extendingthe one of the plurality of shafts of the second transmission on theside of the housing opposite to the belt transmission so as to avoidinterference with the belt transmission.

These, further and other objects, features and advantages of theinvention will appear more fully from the following detailed descriptionwith reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a skeleton diagram of a hybrid vehicle V1 equipped with a pairof electric transaxles ET1 for driving front wheels 14 and with anengine-transmission assembly 20 for driving rear wheels 24.

FIG. 2 is a plan view partly in section of electric transaxle ET1 usedfor vehicle V1.

FIG. 3 is a sectional plan view of engine-transmission assembly 20 usedfor vehicle V1.

FIG. 4 is a side view partly in section of an electric transaxle ET2.

FIG. 5 is a schematic side view of an electric utility vehicle V2equipped with electric transaxle ET2 serving as a rear transaxle fromwhich power is taken and transmitted into a front transaxle casing via apropeller shaft.

FIG. 6 is a schematic side view of a hybrid utility vehicle V3 equippedwith electric transaxle ET2 serving as a rear transaxle, and equippedwith an engine 80 whose power can be transmitted to the front transaxlecasing or/and electric transaxle ET2 serving as the rear transaxle.

FIG. 7 is a fragmentary schematic side view of vehicle V3 equipped withan electric transaxle ET2 a serving as a modification of electrictransaxle ET2.

FIG. 8 is a side view partly in section of an electric transaxle ET2 bserving as another modification of electric transaxle ET2.

FIG. 9 is a schematic side view pf an electric utility vehicle V4equipped with electric transaxles ET2 b serving as front and reartransaxles.

FIG. 10 is a side view partly in section of an electric transaxle ET2 cserving as a modification of electric transaxle ET2 b.

FIG. 11 is a schematic plan view of a vehicle V5 that is equipped withan engine-transmission assembly 120 carrying rear wheels 24 and that isequipped with a front transaxle 133 carrying front wheels 14, whereinthe front transaxle 133 is driven by power taken off fromengine-transmission assembly 120, and wherein engine-transmissionassembly 120 includes a motor generator.

FIG. 12 is a developed sectional view of engine-transmission assembly120.

FIG. 13 is a sectional view of a governor 141 set at a parking-onposition in engine-transmission assembly 120 when engine 21 isstationary.

FIG. 14 is a sectional view of governor 141 set at a parking-offposition.

FIG. 15 is a sectional view of governor 141 set at parking-off positionwhen engine 21 is driven.

FIG. 16 is a skeleton diagram of a vehicle V6 that is equipped with acentral engine-transmission assembly 220 and front and rear transaxlesdriven by power outputted from central engine-transmission assembly 220,wherein central engine-transmission assembly 220 includes a motorgenerator.

FIG. 17 is a developed sectional view of central engine-transmissionassembly 220.

FIG. 18 is a fragmentary sectional view of central engine-transmissionassembly 220 showing a transmission (first counter) shaft 236 and a forkshaft 280 operatively connected to each other via a fork 241.

FIG. 19 is a fragmentary sectional view of central engine-transmissionassembly 220 showing sensors 281 and 282 for detecting a position offork 241.

FIG. 20 is a fragmentary external view of central engine-transmissionassembly 220 showing sensors 281 and 282.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1, 2 and 3, a hybrid vehicle (hereinafter, simplyreferred to as “vehicle”) V1 will be described. Vehicle V1 is a utilityvehicle, for example. Vehicle V1 is equipped with a pair of electrictransaxles ET1 serving as right and left front transaxles for drivingrespective right and left front wheels 14, and is equipped with anengine-transmission assembly 20 for driving right and left rear wheels24. Engine-transmission assembly 20 is a combination of an engine 21 anda transmission assembly, and the transmission assembly includes atransaxle casing 22, and a belt transmission BT1 for transmitting powerfrom engine 21 into transaxle casing 22. Right and left rear wheels 24are provided on distal ends of respective right and left rear axles 23supported by transaxle casing 22. Transaxle casing 22 incorporates aforward traveling gear train FG, a backward traveling gear train RG, anda differential gear unit D differentially connecting proximal ends ofright and left rear axles 23 to each other. Either forward travelinggear train FG or backward traveling gear train RG is selected totransmit power from belt transmission BT1 to differential gear unit D.

Further, vehicle V1 is equipped with a generator 19 that is driven bydriving engine 21 so as to generate electric power, and is equipped witha battery 18 for reserving the electric power generated by generator 19and for supplying the electric power to electric motors 2 of respectiveelectric transaxles ET1.

Referring to FIGS. 1 and 2, each of right and left electric transaxlesET1 will be described. Electric transaxle ET1 includes a reduction gearcasing 1, an axle 12, an electric motor 2, and a reduction gear trainRG1 disposed in reduction gear casing 1 so as to transmit power fromelectric motor 2 to axle 12.

Axle 12 is journalled by reduction gear casing 1 via a bearing 16, andis extended outward from reduction gear casing 1 through an opening ofreduction gear casing 1 so as to be fixedly provided on a distal endportion thereof with a hub 13 that is fixed to a rim 14 a of front wheel14. The opening of reduction gear casing 1 passing axle 12 therethroughis covered with a cover 1 a. Axle 12 is formed with a flange 12 a on aproximal end portion thereof disposed in reduction gear casing 1, andflange 12 a is journalled by reduction gear casing 1 via a bearing 15.

Electric motor 2 is fastened to reduction gear casing 1 via a bolt 17and so on. A motor output shaft 3 of electric motor 2 is inserted at atip thereof into reduction gear casing 1 and is extended coaxially toaxle 12. Reduction gear train RG1 interposed between motor output shaft3 and axle 12 will be detailed. A motor output gear 4 is fixed on thetip of motor output shaft 3. A sun gear 8 is disposed between the tip ofmotor output shaft 3 and flange 12 a of axle 12 coaxial to motor outputshaft 3 and axle 12. Sun gear 8 is fixedly fitted into a carrier 7 thatis disposed between the tip of motor output shaft 3 and flange 12 a ofaxle 12, so that sun gear 8 is rotatably integral with carrier 7.Carrier 7 is extended from sun gear 8 in a radial direction of motoroutput shaft 3 and axle 12, and pivotally supports a planetary gear 5via a pivot shaft 6 extended parallel to motor output shaft 3 and axle12. Planetary gear 5 meshes with motor output gear 4.

Further, an internal gear 10 is fixed on an inner peripheral surface ofreduction gear casing 1, and planetary gear 5 meshes with internal gear10. On the other hand, flange 12 a of axle 12 pivotally supports aplanetary gear 9 via a pivot shaft 11 extended parallel to motor outputshaft 3 and axle 12. Planetary gear 9 meshes with sun gear 8, and mesheswith internal gear 10. In this way, motor output gear 4, planetary gear5, sun gear 8, planetary gear 9 and internal gear 10 constitutereduction gear train RG1.

Power of electric motor 2 is transmitted to axle 12 via reduction geartrain RG1 in the following way. When motor output gear 4 rotatestogether with motor output shaft 3, planetary gear 5 is rotated by therotation of motor output gear 4 so as to revolve along internal gear 10around an axis of motor output shaft 3. The revolution of planetary gear5 causes rotation of carrier 7 centered on an axis of sun gear 8,thereby causing rotation of sun gear 8 centered on its own axis.Planetary gear 9 is rotated by the rotation of sun gear 8 so as torevolve along internal gear 10 around an axis of axle 12. The revolutionof planetary gear 9 causes rotation of flange 12 a centered on the axisof axle 12, thereby causing rotation of axle 12 centered on its ownaxis. In this way, due to internal gear 10, the rotation of planetarygear 5 following the rotation of motor output gear 4 is converted intothe revolution of planetary gear 5 such as to reduce the rotary speed ofsun gear 8, and then, the rotation of planetary gear 9 following thespeed-reduced rotation of sun gear 8 is converted into the revolution ofplanetary gear 9 such as to further reduce the rotary speed of axle 12.Therefore, reduction gear train RG1 has a great reduction gear ratiowhile ensuring its compactness.

Electric motors 2 of respective right and left electric transaxles ET1are supplied with electric power from battery 18, and their turning onand off and their output rotary speeds are controlled by a controller(not shown) provided in vehicle V1. Especially, to turn vehicle V1, theoutput rotary speeds of electric motors 2 of right and left electrictransaxles ET1 are differentially controlled so as to differentiallyrotate right and left front wheels 14.

Electric motor 2 may be configured as a motor generator whichregenerates kinetic energy into electric energy. Therefore, electricmotor 2 can serve as a regeneration brake. In this regard, electricmotor 2 may be configured so as to be switched on to function as anelectric motor for setting vehicle V1 into the four-wheel drive modewhen a slip of a belt 28 in a later-discussed belt transmission BT1 isdetected.

Engine and transmission system 20 will be detailed with reference toFIGS. 1 and 3. Belt transmission BT1 includes a belt transmission cover25, pulleys 27 and 29 and a belt 28. An engine output shaft 26 of engine21 is extended into belt transmission cover 25 so as to serve as aninput shaft of belt transmission BT1. A transmission input shaft 30 ofthe gear transmission in transaxle casing 22 is extended outward fromtransaxle casing 22 in parallel to engine output shaft 26 and into belttransmission cover 25 so as to serve as an output shaft of belttransmission BT1. In belt transmission cover 25, pulley 27 is providedon engine output shaft 26, pulley 29 is provided on transmission inputshaft 30, and belt 28 is interposed between pulleys 27 and 29. Belttransmission BT1 is a continuously variable transmission (CVT), in whichpulleys 27 and 29 are split pulleys, configured so that a ratio of aradius of a looping portion of belt 28 in pulley 27 round engine outputshaft 26 to a radius of a looping portion of belt 28 in pulley 29 roundtransmission input shaft 30 is variable.

Generator 19 is disposed around engine output shaft 26 in belttransmission cover 25. Generator 19 includes a stator 21 a fixed toengine 21, and includes a rotor 27 a fixed to pulley 27. Stator 21 a isprovided with armature windings 21 b, and rotor 27 a is provided withmagnets 27 b. Stator 21 a and rotor 27 a are disposed so that magnets 27b face armature windings 21 b. Therefore, when stator 27 a rotatestogether with engine output shaft 26, armature windings 27 a are excitedby rotating magnets 27 b so as to generate electric power to be reservedin battery 18.

In transaxle casing 22, transmission input shaft 30, a counter shaft 31,and right and let coaxial axles 23 are extended in parallel and arejournalled by transaxle casing 22 via bearings. In detail, transaxlecasing 22 includes right and left gear housings 22 a and 22 b and rightand left brake housings 22 c and 22 d. Right and left gear housings 22 aand 22 b are joined to each other at a vertical joint plane so as todefine a gear chamber of transaxle casing 22 incorporating forwardtraveling gear train FG, backward traveling gear train RG anddifferential gear unit D. Right brake housing 22 c is joined to rightgear housing 22 a so as to extend rightward from right gear housing 22a, thereby journaling right axle 23 via bearings, and thereby defining aright brake chamber of transaxle casing 22 incorporating a right brake44 for braking right axle 23. Left brake housing 22 d is joined to leftgear housing 22 b so as to extend leftward from left gear housing 22 b,thereby journaling left axle 23 via bearings, and thereby defining aleft brake chamber of transaxle casing 22 incorporating a left brake 44for braking left axle 23. Right and left axles 23 project rightwardlyand leftwardly outward from right and left brake housings 22 c and 22 d,respectively, so as to be provided on respective distal ends thereofwith respective right and left rear wheels 24.

In each of the right and left brake chambers of transaxle casing 22,friction discs that are unrotatable relative to corresponding axle 23and friction discs that are unrotatable relative to transaxle casing 22are alternately aligned so as to constitute each of right and leftbrakes 44. A brake shoe 45 is disposed in each of the right and leftbrake chambers between each brake 44 and each of right and left gearhousings 22 a and 22 b. Right and left brake arms 46 are pivoted onouter portions of respective right and left brake housings 22 c and 22d, and are operatively connected to respective brake shoes 45 and to abrake manipulator (not shown) of vehicle V1. When the brake manipulatoris operated for braking, brake arms 46 are rotated to move respectivebrake shoes 45 toward respective brakes 44 so as to press the frictiondiscs of respective brakes 44 against one another, thereby applyingbrakes 44 to stop right and left axles 23. When the brake manipulator isoperated for unbraking, brake arms 46 are rotated to move respectivebrake shoes 45 away from respective brakes 44 so as to separate thefriction discs of respective brakes 44 from one another, therebyallowing rotation of right and left axles 23 freely from respectivebrakes 44.

In the gear chamber of transaxle casing 22, a centrifugal governor 47 isprovided on transmission input shaft 30. Centrifugal governor 47 detectsthe rotary speed of transmission input shaft 30 (serving as the outputshaft of belt transmission BT1) and controls engine 21 to change therotary speed of engine output shaft 26 (serving as the input shaft ofbelt transmission BT1) in correspondence to the detected rotary speed oftransmission input shaft 30.

In the gear chamber of transaxle casing 22, a forward traveling drivegear 32 and a backward traveling drive gear 33 are formed (or fixed) ontransmission input shaft 30. In the gear chamber of transaxle casing 22,a forward traveling driven gear 34 and a backward traveling driven gear35 are fitted on counter shaft 31 so as to be rotatable relative tocounter shaft 31. Forward traveling drive gear 32 and forward travelingdriven gear 34 mesh with each other so as to constitute forwardtraveling gear train FG. Backward traveling drive gear 33 and backwardtraveling driven gear 35 mesh with an idle gear (not shown) so thatbackward traveling drive gear 33, the idle gear and backward travelingdriven gear 35 constitute backward traveling gear train RG. Further, apinion 37 is formed (or fixed) on counter shaft 31 so as to transmit therotary force of counter shaft 31 to later-discussed differential gearunit D.

Counter shaft 31 is formed with a spline portion between gears 34 and35, and a reverser shifter 36 is spline-fitted on the spline portion ofcounter shaft 31 so that reverser shifter 36 is unrotatable relative tocounter shaft 31 and is axially slidable on counter shaft 31. Gears 34and 35 are formed with notches in respective portions thereof facingreverser shifter 36. Reverser shifter 36 is formed on axial oppositeends thereof with teeth to be fitted into the notches of respectivegears 34 and 35. The notches of forward traveling driven gear 34 and theteeth on one end of reverser shifter 36 facing forward traveling drivengear 34 constitute a dog clutch for forward traveling rotation of axles23. The notches of backward traveling driven gear 35 and the teeth onthe other end of reverser shifter 36 facing backward traveling drivengear 35 constitute a dog clutch for backward traveling rotation of axles23.

Reverser shifter 36 can be shifted among a forward traveling position, aneutral position and a backward traveling position. When reversershifter 36 is disposed at the forward traveling position, the teeth onone end of reverser shifter 36 are fitted into the notches of forwardtraveling driven gear 34 so as to rotatably integrate forward travelingdriven gear 34 with counter shaft 31 via reverser shifter 36, so thatthe rotary force of transmission input shaft 30 driven by engine 21 viabelt transmission BT1 is transmitted to counter shaft 31 via forwardtraveling gear train FG, thereby rotating axles 23 in the forwardtraveling rotation direction of rear wheels 24. When reverser shifter 36is disposed at the backward traveling position (as shown in FIG. 3), theteeth on the other end of reverser shifter 36 are fitted into thenotches of backward traveling driven gear 35 so as to rotatablyintegrate backward traveling driven gear 35 with counter shaft 31 viareverser shifter 36, so that the rotary force of transmission inputshaft 30 is transmitted to counter shaft 31 via backward traveling geartrain RG, thereby rotating axles 23 in the backward traveling rotationdirection of rear wheels 24. When reverser shifter 36 is disposed at theneutral position (as shown in FIG. 1), neither forward traveling drivengear 34 nor backward traveling driven gear 35 has the teeth of reversershifter 36 in the notches thereof, so that gears 34 and 35 are allowedto rotate relative to counter shaft 31, thereby preventing the rotaryforce of transmission input shaft 30 from being transmitted to countershaft 31, and thereby making axles 23 free from the power of engine 21.

In the gear chamber of transaxle casing 22, differential gear unit Ddifferentially connects proximal end portions of right and left axles 23to each other. Differential gear unit D includes a differential inputgear (bull gear) 38, a differential casing 39, a pivot shaft 40, beveldifferential pinions 41 and right and left bevel differential side gears42. Right and left axles 23 are journalled by respective right and leftgear housings 22 a and 22 b via respective bearings and are extended atthe respective proximal ends thereof into the gear chamber of transaxlecasing 22 so as to be inserted into differential casing 39, so thataxles 23 are rotatable relative to differential casing 39. Indifferential casing 39, right and left bevel differential side gears 42are fixed on the proximal ends of respective right and left axles 23.

Differential input gear 38 is fixed on differential casing 39 and mesheswith pinion 37 on counter shaft 31. Pivot shaft 40 is extended in aradial direction of axles 23, and is fixed to differential casing 39 soas to be rotatably integral with differential casing 39 and differentialinput gear 38. Bevel differential pinions 41 are pivoted on pivot shaft40. Each of bevel differential pinions 41 meshes with both right andleft differential side gears 42.

Due to the above-mentioned structure, transmission input shaft 30receives the power of engine 21 via belt transmission BT1, and intransaxle casing 22, either forward traveling gear train FG or backwardtraveling gear train RG is selected by reverser shifter 36 so as totransmit the power of engine 21 from transmission input shaft 30 tocounter shaft 31, thereby transmitting the power of engine 21 fromcounter shaft 31 to right and left rear wheels 24 via pinion 37,differential gear unit D and right and left axles 23.

As understood from the above-mentioned structure and FIG. 1, vehicle V1is provided with neither means for distributing the power of engine 21to front wheels 14 nor means for distributing the power of electricmotors 2 to rear wheels 24. This is because vehicle V1 rather setsimportance on the advantages in structural simplicity and reduction ofcomponents and costs. Assumptive driving modes of vehicle V1 are twotypes of 2WD (two wheel drive) mode: a first 2WD mode to drive vehicleV1 by driving only rear wheels 24 by power of engine 21; and a second2WD mode to drive vehicle V1 by driving only front wheels 14 by power ofelectric motors 2.

In this regard, vehicle V1 is provided with a mode selection means,e.g., a switch, a button, a dial, a lever or a pedal, which is operatedto select either the first 2WD mode where only rear wheels 24 are drivenby engine 21 or the second 2WD mode where only front wheels 14 aredriven by electric motors 2. Therefore, an operator who drives vehicleV1 can optionally select either the first 2WD for obtaining silence orthe second 2WD for obtaining high power.

Various changes and modifications may be made in vehicle V1. Forexample, vehicle V1 may be alternatively provided withengine-transmission assembly 20 for driving right and left front wheels14 and with the pair of electric transaxles ET1 for driving right andleft rear wheels 24. Further, it is possible that vehicle V1 can travelin 4WD (four wheel drive) mode, where front wheels 14 are driven byelectric motors 2 of electric transaxles ET1 and simultaneously rearwheels 24 are driven by engine 21 of engine-transmission assembly 20, ifrotary speeds of front wheels 14 and rear wheels 24 can be equalizedwell. Incidentally, if vehicle V1 is provided with means, e.g., apropeller shaft and universal joints, for transmitting power fromelectric motors 2 to rear wheels 24 and/or for transmitting power fromengine 21 to front wheels 14, front wheels 14 can be driven by combinedpowers of electric motors 2 and engine 21 and/or rear wheels 24 can bedriven by combined powers of engine 21 and electric motors 2.

Referring to FIG. 4, an electric transaxle ET2 will be described.Electric transaxle ET2 is defined as a transaxle integrated with anelectric motor 51. Electric transaxle ET1 includes a reduction gearcasing 52, a differential gear casing 53, and a power taking-off (PTO)casing 54. Reduction gear casing 52 includes a main housing 52 a and acover 52 b joined to each other. Electric motor 51 and differential gearcasing 53 are fixed to main housing 52 a of reduction gear casing 52 soas to be cantilevered from reduction gear casing 52 in the samedirection. PTO casing 54 is fixed to cover 52 b of reduction gear casing52 so as to extend from reduction gear casing 52 opposite to electricmotor 51 and differential gear casing 53. Hereinafter, it is assumedthat electric motor 51 and differential gear casing 53 are extendedrearward from reduction gear casing 52, and PTO casing 54 is extendedforward from reduction gear casing 52.

Electric motor 51 has a motor output shaft 51 a that is extended intoreduction gear casing 52. A motor output pinion 51 b is fixed on motoroutput shaft 51 a in reduction gear casing 52. A gear member 55 isformed with a cup-shaped portion and with an axial shaft 55 a extendedfrom the cup-shaped portion thereof. Gear member 55 is disposed inreduction gear casing 52 so as to have axial shaft 55 a journalled bycover 52 a via bearings 66. Axial shaft 55 a of gear member 55 isextended in the axial direction of motor output shaft 51 a. However,axial shaft 55 a is axially offset from motor output shaft 51 a in theradial direction of motor output shaft 51 a, i.e., axial shaft 55 a isnot coaxial to motor output shaft 51 a.

An inner peripheral surface of the cup-shaped portion of gear member 55is toothed to form an inner peripheral gear 55 b, and an outerperipheral surface of the cup-shaped portion of gear member 55 istoothed to form an outer peripheral gear 55 c. Motor output shaft 51 ais inserted into the cup-shaped portion of gear member 55 so that motoroutput pinion 51 b meshes with inner peripheral gear 55 b of gear member55.

Motor output pinion 51 b and inner peripheral gear 55 b constitute areduction gear train that is advantageous in its compactness and itslarge reduction gear ratio. More specifically, when viewed in the axialdirection of motor output shaft 51 a and axial shaft 55 a, motor outputpinion 51 b is disposed within a circle defined by inner peripheral gear55 b, thereby achieving the compactness, especially, minimizing the geararrangement in radial directions of axial shaft 55 a. Further, even inthe case that the diametrical size of gear member 55 (i.e., the diameterof inner peripheral gear 55 b) is limited, the diametrical differencebetween motor output pinion 51 b and inner peripheral gear 55 b can beincreased by reducing the diametrical size of motor output pinion 51 b,thereby ensuring a large reduction gear ratio as well as thecompactness.

However, it should be considered that as the diametrical size of motoroutput pinion 51 b is reduced, the axial offset degree of electric motor51 from gear member 55 (i.e., the deviation of motor output shaft 51 afrom axial shaft 55 a in the radial direction of gear member 55) isincreased. Therefore, to allow the diametrical size reduction of motoroutput pinion 51 b relative to inner peripheral gear 55 b for ensuringthe large reduction gear ratio, electric transaxle ET2 is configured sothat electric motor 51 can be mounted on a portion of reduction gearcasing 52 such as to ensure the required axial offset degree of electricmotor 51 from gear member 55 in reduction gear casing 52.

A final reduction gear 56 is disposed in reduction gear casing 52 andmeshes with outer peripheral gear 55 c of gear member 55. As a result,motor output pinion 51 b, inner peripheral gear 55 b, outer peripheralgear 55 c and final reduction gear 56 constitute an entire reductiongear train RG2 in reduction gear casing 52. Final reduction gear 56 isfixed on a reduction output shaft 57. Reduction output shaft 57 isjournalled by main housing 52 a of reduction gear casing 52 via abearing 67, and is journalled by cover 52 b of reduction gear casing 52via a bearing 68 so as to extend in the axial direction of motor outputshaft 51 a. A rear end portion of reduction output shaft 57 is insertedinto differential gear casing 53 via main housing 52 a of reduction gearcasing 52. A bevel pinion 57 a is formed on the rear end portion ofreduction output shaft 57 in differential gear casing 53.

A differential gear unit 58 is disposed in differential gear casing 53so as to differentially connect proximal ends of right and left axles 59to each other. Differential gear unit 58 has a bevel input gear 58 athat meshes with bevel pinion 57 a. Right and left axles 59 arejournalled by differential gear casing 53 and are extended rightwardlyand leftwardly (perpendicular to the axial direction of motor outputshaft 51 a) outward from differential gear casing 53.

PTO casing 54 is formed in a rear portion thereof with a clutch chamber54 a, and is formed in a front portion thereof with a PTO shaft chamber54 b that is opened forwardly outward. A PTO shaft 61 is journalled viaa bearing 69 by a partitioning wall of PTO casing 54 formed betweenchambers 54 a and 54 b. A rear end portion 61 b of PTO shaft 61 issplined on an outer peripheral surface thereof, and is formed thereinwith a rearwardly opened recess 61 a. Rear end portion 61 b of PTO shaft61 is disposed in clutch chamber 54 a. A front end portion 61 c of PTOshaft 61 is splined on an outer peripheral surface thereof, and isdisposed in PTO chamber 54 b. A front portion 57 b of reduction outputshaft 57 is splined on an outer peripheral surface thereof, and isdisposed in clutch chamber 54 a. A front end projection 57 c that isdiametrically smaller than splined front portion 57 b of reductionoutput shaft 57 projects forward from splined front portion 57 b, and isinserted into recess 61 a of PTO shaft 61 in clutch chamber 54 a, sothat reduction output shaft 57 is rotatable relative to PTO shaft 61.

A clutch 60 is interposed between reduction output shaft 57 and PTOshaft 61 in clutch chamber 54 a. Clutch 60 includes a clutch slider 62,a spline hub 63, a detent assembly 64 and a spacer 65. Spline hub 63 isfixed on splined front portion 57 b of reduction output shaft 57, andspacer 65 is fixed on reduction output shaft 57 between spline hub 63and cover 52 b of reduction gear casing 52. Clutch slider 62 is fittedon the splined outer peripheral surface of rear end portion 61 b of PTOshaft 61 so as to be axially slidable on PTO shaft 61 and so as to beunrotatable relative to PTO shaft 61. Detent assembly 64 includes a pairof balls and a compressed spring sandwiched between the balls, and isfitted in a diametric through hole of PTO shaft 61, so that the ballsare pressed against clutch slider 62 by the spring.

Clutch slider 62 can be shifted between a clutch-on position and aclutch-off position, and can be held at either the clutch-on position orthe clutch-off position by detent assembly 64. When clutch slider 62 isdisposed at the clutch-on position, clutch slider 62 meshes with splinehub 63 (as shown in FIG. 4) so that PTO shaft 61 is rotatably integratedwith reduction output shaft 57 so as to receive the output of electricmotor 51. When clutch slider 62 is disposed at the clutch-off position,clutch slider 62 does not mesh with spline hub 63 so that PTO shaft 61is rotatably free from reduction output shaft 57 so as to be isolatedfrom the output of electric motor 51.

Referring to FIGS. 4 and 5, an electric utility vehicle (hereinafter,simply referred to as “vehicle”) V2 equipped with electric transaxle ET2will be described. Vehicle V2 has a vehicle body frame 71 extended froma front end thereof to a rear end thereof. A rear portion of vehiclebody frame 71 is formed as a base 150, and a load carrying bed 101 ismounted on a top of base 150. A front portion of base 150 projectsforward from load carrying bed 101 when viewed in plan, and anoperator's seat 102 is mounted on this front portion of bed 150 so as tobe disposed immediately forward of load carrying bed 101. Base 150 isopen at the top thereof, and load carrying bed 101 and seat 102 arerotatable vertically in the fore-and-aft direction so that a spacedefined by base 150 can be opened upward by rotating load carrying bed101 and seat 102.

Electric transaxle ET2 is disposed in the space defined by base 150under load carrying bed 101 so as to serve as a rear transaxlesupporting right and left rear axles 59, and right and left rear wheels72 are drivingly connected to distal ends of respective right and leftaxles 59 via respective suspensions. In this regard, as shown in FIG. 4,differential gear casing 53 of electric transaxle ET2 is formed withbosses 53 a and 53 b, and is fastened to vehicle body frame 71 via bolts70 passed through respective bosses 53 a and 53 b, thereby mountingelectric transaxle ET2 onto vehicle body frame 71. Further, electrictransaxle ET2 is disposed so as to extend electric motor 51 anddifferential gear casing 53 supporting right and left axles 59 rearwardfrom reduction gear casing 52 so that electric motor 51 and differentialgear casing 53 are vertically offset from each other (more specifically,electric motor 51 is disposed above differential gear casing 53) so asto overlap each other when viewed in plan and so that PTO casing 54,incorporating PTO clutch 60 and PTO shaft 61, extends forward fromreduction gear casing 52.

In other words, transaxle ET2 is disposed below load carrying bed 101 soas to overlap load carrying bed 101 when viewed in plan. Therefore, thedead space under load carrying bed 101 is utilized for arrangingtransaxle ET2 so as to expand a later-discussed operator's space forwardof load carrying bed 101 while ensuring compactness of entire vehicleV2.

Further, reduction gear casing 52 and differential gear casing 53constitute a transaxle casing of transaxle ET2. Reduction gear casing 52serves as a portion of the transaxle casing incorporating a drive trainfor transmitting power of electric motor 51 to axles 59. Differentialgear casing 53 serves as a portion of the transaxle casing supportingaxles 59. In other words, electric motor 51 and the portion of thetransaxle casing incorporating axles 59 are extended from the portion ofthe transaxle casing incorporating the drive train so as to bevertically offset from each other and so as to overlap each other whenviewed in plan. The rearwardly horizontal extension of electric motor 51and differential gear casing 53 from reduction gear casing 52 isadvantageous for vertically minimizing transaxle ET2, and the verticaloffsetting of electric motor 51 and differential gear casing 53overlapping each other when viewed in plan is advantageous forhorizontally (fore-and-aft or laterally) minimizing transaxle ET2.

Also, at least one battery 100 for reserving electric power to besupplied to electric motor 51 of transaxle ET2 is disposed in the spacedefined by base 150 of vehicle V2. In other words, battery (batteries)100 is disposed below load carrying bed 101 or seat 102 so as to overlapload carrying bed 101 or seat 102 when viewed in plan. In this regard,there is a sufficient room for arranging battery (batteries) 100 in thespace defined by base 150 forward of transaxle ET2 that is minimized inthe fore-and-aft direction by the vertical offsetting of differentialgear casing 53 and electric motor 51 overlapping each other when viewedin plan. Therefore, the dead space in base 150 under load carrying bed101 and seat 102 is utilized for arranging battery (batteries) 100 so asto expand an available space in vehicle V2 such as the operator's spaceinvolving seat 102 forward of load carrying bed 101 while ensuring thecompactness of entire vehicle V2.

For example, load carrying bed 101 is rotatable at a front end thereofrearwardly upward centered on a rear end thereof, and seat 102 isrotatable at a rear end thereof forwardly upward centered on a front endthereof. The space in base 150 can be easily opened upward by upwardlyrotating load carrying bed 101 and seat 102 so as to be convenient foraccess to electric transaxle ET2 and battery (or batteries) 100 in thespace for exchanging or maintenance. Further, electric motor 51 extendedrearward from reduction gear casing 52 is attachable and detachable toand from reduction gear casing 52, and vehicle V2 is configured so thata man's hand can be easily inserted into the space in base 150 via arear end of vehicle body frame 71 defining the rear end of base 150 soas to handle electric motor 51. In this embodiment of FIG. 5 and inlater-discussed embodiments of FIGS. 6, 7 and 9, a vertical plate-shapedrear end portion 71 a of vehicle body frame 71 is formed as a hingeddoor that can be rotated rearward. Alternatively, rear end portion 71 amay be vertically slidable, or a small window through which electricmotor 51 can be passed may be provided in the rear end of vehicle bodyframe 71.

Vehicle V2 is further equipped at the front end portion thereof with afront transaxle casing 75 supporting right and left front axles 77, andright and left front wheels 78 are drivingly connected to distal ends ofrespective right and left front axles 77. Front transaxle casing 75incorporates a differential unit (not shown) differentially connectingright and left front axles 77 to each other. Front transaxle casing 75,the differential unit in front transaxle casing 75 and axles 77supported by front transaxle casing 75 constitute a front transaxle.Incidentally, a casing incorporating a differential unit, which isidentical to differential gear casing 53 for constituting transaxle ET2,may serve as front transaxle casing 75 incorporating the differentialunit for constituting the front transaxle. An input shaft 76 of thedifferential unit in front transaxle casing 75 projects rearward fromfront transaxle casing 75, and is drivingly connected to front endportion 61 c of PTO shaft 61 of electric transaxle ET2 serving as therear transaxle via at least one propeller shaft 74 and universal joints73.

A steering wheel 103 for steering right and left steerable front wheels78 is disposed forward of seat 102, so that vehicle V2 has an operator'sspace involving seat 102 and steering wheel 102 forward of load carryingbed 101. As mentioned above, both battery (batteries) 100 and electrictransaxle ET2 are accommodated in the space in base 150 under loadcarrying bed 101 and seat 102 so that battery (batteries) 100 disposedforward of electric transaxle ET2 overlaps load carrying bed 101 or seat102 so as not to project forward from the dead space under seat 102,thereby ensuring the sufficiently large operator's space forward of loadcarrying bed 101.

Further, an end of battery 100 toward the front transaxle, i.e., a frontend of battery 100 (if a plural of batteries 100 are provided, a frontend of foremost battery 100) is disposed in the space in base 150 so asto be closer to a front end of electric transaxle ET2 serving as therear transaxle than a rear end of front transaxle casing 75 serving asthe front transaxle. In other words, a distance of the front transaxle(front transaxle casing 75) from the front end of battery 100 is longerthan a distance of the rear transaxle (electric transaxle ET2) from thefront end of battery 100. The longer distance of the front transaxlefrom the front end of battery 100 generally defines the fore-and-aftlength of the operator's space. Therefore, the arrangement of the frontend of battery 100 closer to the rear transaxle is advantageous forexpanding the operator's space in the fore-and-aft direction.

In this way, vehicle V2 is driven by only the electric power fromelectric motor 51. Vehicle V2 can be driven in a four-wheel drive (4WD)mode where both rear wheels 72 and front wheels 78 are driven by settingclutch slider 62 of clutch 60 at the clutch-on position, and vehicle V2can be driven in a two-wheel drive (2WD) mode where only rear wheels 72are driven by setting clutch slider 62 of clutch 60 at the clutch-offposition.

Further, the output rotary speed of electric motor 51 is variable sothat vehicle V2 can travel at various speeds, and the output rotarydirection of electric motor 51 is reversible so that vehicle V2 cantravel forward and backward.

Referring to FIGS. 4 and 6, a hybrid utility vehicle (hereinafter,simply referred to as “vehicle”) V3 equipped with electric transaxle ET2will be described. The same reference numerals as those used in FIG. 5designate members that are identical to the above-mentioned members inthe embodiment of FIG. 5 or have the same functions as mentioned above.Vehicle V3 is equipped with electric transaxle ET2 supporting rearwheels 72, and is equipped with front transaxle casing 75 supportingfront wheels 78, similar to vehicle V2. In the space defined by base 150under load carrying bed 101 and seat 102, engine 80 is mounted onvehicle body frame 71 so that electric motor 51 of electric transaxleET2 and engine 80 serve as prime movers for driving wheels 72 and 78 ofvehicle V3. Further, vehicle V3 is equipped with at least battery 100for reserving electric power to be supplied to electric motor 51.

Further, in the space defined by base 150, a transmission casing 86 ismounted on vehicle body frame 71. It appears in FIG. 6 that engine 80 isdisposed above transmission casing 86, however, this arrangement is onlyfor convenience to expression of engine 80 and transmission casing 86 inFIG. 6. In fact, engine 80 and transmission casing 86 may be juxtaposedright and left. Transmission casing 86 incorporates a transmissionmechanism (not shown) such as a gear transmission. An engine outputshaft 81 of engine 80 and a transmission input shaft 85 of thetransmission mechanism in transmission casing 86 are extended parallelto each other.

Since engine 80 and transmission casing 86 are disposed in the space inbase 150, each of engine 80 and transmission casing 86 is disposed belowload carrying bed 101 or seat 102 so as to overlap load carrying bed 101or seat 102 when viewed in plan. In this regard, each of engine 80 andtransmission casing 86 may be disposed so as to be covered with bothload carrying bed 101 and seat 102 (i.e., covered at a part thereof withload carrying bed 101 and at another part thereof with seat 102) or soas to be entirely covered with only load carrying bed 101 or with onlyseat 102. Therefore, the dead space in base 150 below load carrying bed101 and seat 102 is utilized for arranging engine 81 and transmissioncasing 86 so as to ensure the operator's space of vehicle V3 with seat102 and steering wheel 103.

A belt transmission BT2 is interposed between engine output shaft 81 andtransmission input shaft 85 Belt transmission BT2 includes a pulley 82provided on engine output shaft 81, a pulley 84 provided on transmissioninput shaft 85, and a belt 83 interposed between pulleys 82 and 84. Dueto the above-mentioned arrangement of engine 81 and transmission casing86, belt transmission BT2 is also disposed in the space in base 150under load carrying bed 101 and seat 102 so as not to project forwardinto the operator's space of vehicle V3.

Similar to the space in base 150 of vehicle V1, the space in base 150 ofvehicle V2 can be opened upward by upwardly rotating load carrying bed101 and seat 102 so as to be convenient for access to the members in thespace, i.e., electric transmission ET2, battery 100, engine 80,transmission casing 86 and belt transmission BT2 for maintenance oranother purpose.

Belt transmission BT2 is a continuously variable transmission (CVT)serving as a main speed changing transmission, and the transmission intransmission casing 86 is a variable speed transmission that is a subspeed changing transmission driven by the main speed changingtransmission. Alternatively, only one of belt transmission BT2 and thetransmission in transmission casing 86 may have variable speeds.Therefore, vehicle V3 can travel at various speeds when it is driven bypower of electric motor 51 as well as power of engine 80.

A transmission output shaft 87 of the transmission in transmissioncasing 86 projects at a rear end portion thereof rearwardly outward fromtransmission casing 86, and projects at a front end portion thereofforwardly outward from transmission casing 86. Vehicle V3 is providedwith a not-shown clutch (hereinafter, referred to as “engine clutch”),which is clutched on to transmit power from engine 80 to transmissionoutput shaft 87, and which is clutched off to isolate transmissionoutput shaft 87 from the power of engine 80 (in other words, to isolateengine 80 from rotational force of transmission output shaft 87). Theengine clutch is disposed on any portion of the power train betweenengine 80 and transmission output shaft 87. For example, the engineclutch may be a tension clutch in belt transmission BT2, or the engineclutch may be interposed between engine output shaft 81 and pulley 82 orbetween transmission input shaft 85 and pulley 84, or a shifter of thetransmission in transmission casing 86 may serve as the engine clutch.

The transmission in transmission casing 86 is provided with a reverser(not shown) for reversing the rotational direction of transmissionoutput shaft 87, while the rotational direction of engine output shaft81 is constant. Therefore, vehicle V3 can travel either forward orbackward depending on selection of the rotational direction of motoroutput shaft 51 a in electric transaxle ET2 when vehicle V3 is driven bythe power of electric motor 51, and vehicle V3 can travel either forwardor backward depending on operation of the reverser in transmissioncasing 86 for selecting the rotational direction of transmission outputshaft 87 when vehicle V3 is driven by the power of engine 80.

The front end portion of transmission output shaft 87 is drivinglyconnected to input shaft 76 projecting rearward from front transaxlecasing 75 via at least one propeller shaft 74 and universal joints 73.

The rear end portion of transmission output shaft 87 is drivinglyconnected to PTO shaft 61 via a coupler 88. For example, coupler 88 is asleeve whose inner peripheral surface is splined, and the rear endportion of transmission output shaft 87 is splined on the outerperipheral surface thereof, so that the splined rear portion oftransmission output shaft 87 and above-mentioned splined front endportion 61 c of PTO shaft 61 are spline-fitted into coupler 88, therebyrotatably integrating reduction output shaft 57 and PTO shaft 61 withtransmission output shaft 87 when clutch 60 is clutched on.Alternatively, a universal joint or a propeller shaft with universaljoint may be interposed between transmission output shaft 87 and PTOshaft 61 so as to drivingly connect transmission output shaft 87 to PTOshaft 61.

In vehicle V3, PTO shaft 61 for transmitting power of electric motor 51to front wheels 72 also serves as an input shaft of electric transaxleET2 for receiving power from engine 80.

When clutch 60 is clutched on, vehicle V3 travels in 4WD mode where rearwheels 72 and front wheels 78 are driven by only the power of electricmotor 51, by only the power of engine 80, or by the powers of bothelectric motor 51 and engine 80. On the assumption that clutch 60 isclutched on, vehicle V3 travels in the 4WD mode by only the power ofelectric motor 51 when electric motor 51 is driven to drive motor outputshaft 51 a, and the engine clutch is clutched off regardless of whetherengine 80 is driven or not. At this time, PTO shaft 61 transmits powerof electric motor 51 to front wheels 78 via transmission output shaft 87and at least one propeller shaft 74.

On the same assumption, vehicle V3 travels in the 4WD mode by only thepower of engine 80 when electric motor 51 is not driven to drive motoroutput shaft 51 a, engine 80 is driven and the engine clutch is clutchedon. At this time, the rotary force of transmission output shaft 87driven by engine 80 is distributed to rear wheels 72 via PTO shaft 61,differential gear unit 58 and axles 59, and to front wheels 78 via atleast one propeller shaft 74, input shaft 76, the differential unit infront transaxle casing 75 and axles 77. Further, motor output shaft 51 ais driven by the power of engine 80 via reduction gear train RG2 so thatelectric motor 51 functions as a generator for generating electricpower. The electric power generated by electric motor 51 is reserved inbattery 100 for supplying the electric power to electric motor 51.

On the same assumption, vehicle V3 travels in the 4WD mode by the powersof electric motor 51 and engine 80 when electric motor 51 is driven todrive motor output shaft 51 a, engine 80 is driven and the engine clutchis clutched on. At this time, reduction output shaft 57 receives thepower of electric motor 51 via reduction gear train RG2, and receivesthe power of engine 80 via transmission output shaft 87 and PTO shaft61, so as to transmit the combined power of electric motor 51 and engine80 to rear wheels 72 via differential gear unit 58 and axles 59.Meanwhile, transmission output shaft 87 receives the power of engine 80via belt transmission BT2 and the transmission in transmission casing86, and receives the power of electric motor 51 via reduction gear trainRG2, reduction output shaft 57 and PTO shaft 61, so as to transmit thecombined power of electric motor 51 and engine 80 to front wheels 78 viaat least one propeller shaft 74, input shaft 76 and axles 77. In otherwords, electric motor 51 and engine 80 assist each other to drive frontand rear wheels 78 and 72.

When clutch 60 is clutched off, vehicle V3 travels in 2WD mode whereeither rear wheels 72 or front wheels 78 are driven by only the power ofelectric motor 51 or by only the power of engine 80. On the assumptionthat clutch 60 is clutched off, vehicle V3 travels in the 2WD mode whereonly rear wheels 72 is driven by only the power of electric motor 51when electric motor 51 is driven to drive motor output shaft 51 a, andthe engine clutch is clutched off regardless of whether engine 80 isdriven or not. At this time, reduction output shaft 57 receives thepower of electric motor 51 via reduction gear train RG2 so as to driverear wheels 72, and meanwhile, transmission output shaft 87 drivinglyconnected to front wheels 78 receives neither the power of electricmotor 51 nor the power of engine 80, so that font wheels 78 are notdriven.

On the same assumption, vehicle V3 travels in the 2WD mode where onlyfront wheels 78 are driven by only the power of engine 80 when electricmotor 51 is not driven to drive motor output shaft 51 a, engine 80 isdriven and the engine clutch is clutched on. At this time, the rotaryforce of transmission output shaft 87 driven by engine 80 is transmittedto front wheels 78 via at least one propeller shaft 74, input shaft 76,the differential unit in front transaxle casing 75 and axles 77, andmeanwhile, reduction output shaft 57 receives neither the power ofelectric motor 51 nor the power of engine 80, so that rear wheels 72 arenot driven.

Incidentally, it is possible that vehicle V3 travels in 4WD mode even ifclutch 60 is clutched off. This 4WD mode is set when clutch 60 isclutched off, electric motor 51 is driven to drive motor output shaft 51a, engine 80 is driven, and the engine clutch is clutched on. In this4WD mode, rear wheels 72 are driven by only the power of electric motor51 via reduction gear train RG2, and front wheels 78 are driven by onlythe power of engine 80 via transmission output shaft 87, because clutch60 is clutched off to isolate reduction output shaft 57 from the powerof engine 80 and to isolate transmission output shaft 87 from the powerof electric motor 51. However, the rotary speed of rear wheels 72 drivenby electric motor 51 and the rotary speed of front wheels 78 driven byengine 80 have to be controlled to be equal to each other.

The above-mentioned driving modes of vehicle V3 may be automaticallyselected by a controller based on detection of rotary speed of wheels 72or 78, for example, and/or may be optionally selected by an operator. Inthis regard, vehicle V3 may be provided with a mode selection means forthe optional selection of driving modes, e.g., a switch, a dial, abutton a lever or a pedal. FIG. 6 illustrates a lever 105 serving as themode selection means.

Referring to FIG. 7, an electric transaxle ET2 a is a modification ofelectric transaxle ET2. A chain transmission 89 is disposed in reductiongear casing 52 so as to replace reduction gear train RG2 in reductiongear casing 52 of electric transaxle ET2. Chain transmission 89 includesa sprocket 90 provided on motor output shaft 51 a, a sprocket 92provided on reduction output shaft 57, and a chain 91 interposed betweensprockets 90 and 92. FIG. 7 shows electric transaxle ET2 a used inhybrid vehicle V3. In FIG. 7, the same reference numerals as those usedfor electric transaxle ET2 shown in FIG. 4 and vehicle V3 shown in FIG.6 are used to designate the same components as those of electrictransaxle ET2 and vehicle V3. Alternatively, electric transaxle ET2 amay be used in electric vehicle V2.

Alternatively, chain transmission 89 may be replaced with a belttransmission or a transmission of another type. Incidentally, reductiongear train RG1 in electric transaxle ET1 shown in FIGS. 1 and 2 may bereplaced with a chain transmission, a belt transmission or atransmission of another type.

Referring to FIG. 8, an electric transaxle ET2 b is an alternativemodification of electric transaxle ET2. Electric transaxle ET2 bcorresponds to electric transaxle ET2 without PTO casing 54 and interiorcomponents of PTO casing 54, such as PTO clutch 60 and PTO shaft 61. Inthis regard, in electric transaxle ET2 b, an axial end of reductionoutput shaft 57 opposite to bevel pinion 57 a is disposed in reductiongear casing 52, and cover 52 b covers this end of reduction output shaft52. ET2 b having no PTO shaft 61 is available as a transaxle for drivingonly its own axles 59, which is not assumed to drive another axle. InFIG. 8, the same reference numerals as those used for electric transaxleET2 shown in FIG. 4 are used to designate the same components as thoseof electric transaxle ET2.

Electric transaxle ET2 b includes reduction gear train RG2, similar toelectric transaxle ET2. Alternatively, electric transaxle ET2 b may beprovided with a chain transmission replacing reduction gear train RG2,similar to electric transaxle ET2 a. Alternatively, electric transaxleET2 b may be provided with a belt transmission or another transmissionfor transmitting power of electric motor 51 to differential gear unit58.

Referring to FIG. 9, an electric utility vehicle (hereinafter, simplyreferred to as “vehicle”) V4 is equipped with two electric transaxlesET2 b serving as front and rear transaxles. One electric transaxle ET2 bis supported by a rear portion of vehicle body frame 71 so as to serveas the rear transaxle having right and left axles 59 on which right andleft rear wheels 72 are provided. The other electric transaxle ET2 b issupported by a front portion of vehicle body frame 71 so as to serve asthe front transaxle having right and left axles 59 on which right andleft front wheels 78 are provided. Therefore, rear wheels 72 and frontwheels 78 are driven by independent electric motors 51, i.e., rearwheels 72 are driven by electric power of electric motor 51 of rearelectric transaxle ET2 b, and front wheels 78 are driven by electricpower of electric motor 51 of front electric transaxle ET2 b. Further,vehicle V4 is equipped with at least one battery 100 for reservingelectric power to be supplied to electric motors 51 of front and rearelectric transaxles ET2 b.

Vehicle V4 is driven in either 4WD mode or 2WD mode by only electricpower, similar to vehicle V2. However, the 4WD/2WD mode selection ofvehicle V4 depends on selection whether to drive both or one of electricmotors 51 of front and rear electric transaxles ET2 b, in comparisonwith the 4WD/2WD mode selection of vehicle V2 that depends on shift ofclutch 60 for selecting whether or not the power of electric motor 51 ofelectric transaxle ET2 serving as the rear transaxle is transmitted tofront transaxle casing 75. Further, vehicle V4 can travel in 2WD mode bydriving either rear wheels 72 or front wheels 78 depending on whetherrear electric transaxle ET2 b or front electric transaxle ET2 b isselected to drive its own electric motor 51, in comparison with the 2WDmode traveling of vehicle V2 that depends only on driving of rear wheels72 because front wheels 78 cannot receive power of electric motor 51 ofelectric transaxle ET2 when clutch 60 is clutched off.

Therefore, in comparison with vehicle V2 that needs at least onepropeller shaft 74 and universal joints 73 for transmitting power fromelectric transaxle ET2 having rear axles 59 to front axles 77, vehicleV4 is advantageous in needing no component for transmitting power fromone electric transaxle ET2 b to axles 59 of another electric transaxleET2 b, thereby expanding a free space between front and rear transaxlesET2 b, and thereby eliminating noise that is caused by driving propellershaft 74.

Incidentally, in illustrated vehicle V4, front and rear transaxles ET2 bare arranged so as to be symmetrical in the fore-and-aft direction ofvehicle V4, i.e., one transaxle ET2 b corresponds to the other transaxleET2 b reversed in the fore-and-aft direction of vehicle V4. Morespecifically, front transaxle ET2 b is disposed so as to have electricmotor 51 and differential gear casing 53 extended forward from reductiongear casing 52, and rear transaxle ET2 b is disposed so as to haveelectric motor 51 and differential gear casing 53 extended rearward fromreduction gear casing 52. However, it is not limiting for each of frontand rear transaxles ET2 b whether to extend electric motor 51 anddifferential gear casing 53 forward from reduction gear casing 52 orrearward from reduction gear casing 52.

Referring to FIG. 10, an electric transaxle ET2 c is a modification ofelectric transaxle ET2 b. Electric transaxle ET2 c corresponds toelectric transaxle ET2 b without reduction gear casing 52 and interiorcomponents of reduction gear casing 52, such as reduction gear trainRG2. In this regard, in electric transaxle ET2 c, an electric motor 151is directly attached to differential gear casing 53. Electric motor 151has a motor output shaft 151 a, and a bevel pinion 151 b is formed on atip portion of motor output shaft 151 a. By attaching electric motor 151to differential gear casing 53, motor output shaft 151 is inserted intodifferential gear casing 53 so as to serve as reduction output shaft 57of electric transaxle ET2 b, and bevel pinion 151 b meshes with bevelinput gear 58 a of differential gear unit 58 in differential gear casing53 so as to serve as bevel pinion 57 a of electric transaxle ET2 b.

Electric transaxle ET2 c is advantageous in its compactness and in itsefficiency of power transmission to axles 59, in comparison withelectric transaxle ET2 b having reduction gear casing 52 and reductiongear train RG2.

In vehicle V4 as shown in FIG. 9, at least one of front and rearelectric transaxles ET2 b may be replaced with alternative electrictransaxle ET2 c. Further, electric transaxle ET2 c may be modified tohave a PTO shaft, thereby being able to serve as electric transaxle ET2in electric vehicle V2 or electric transaxle ET2 in hybrid vehicle V3.

Referring to FIG. 11, four-wheel drive vehicle V5, e.g., a utilityvehicle, is equipped with an engine-transmission assembly 120 carryingright and left rear wheels 24. Vehicle V5 is also equipped with a fronttransaxle 133 carrying right and left front wheels 14.Engine-transmission assembly 120 includes a PTO shaft 128 from whichpower is taken off to drive front transaxle 133.

Engine-transmission assembly 120 is a combination of engine 21 and atransmission assembly, and the transmission assembly includes atransaxle casing 122 and a belt transmission casing 125. Transaxlecasing 122 incorporates a gear transmission. Belt transmission casing125 is interposed between engine 21 and transaxle casing 122. Transaxlecasing 122 supports right and left axles 23. Right and left rear wheels24 are provided on distal ends of respective right and left axles 23.

Engine 21 and transaxle casing 122 are juxtaposed in the fore-and-aft orvertical direction of vehicle V5. Belt transmission casing 125 isdisposed on either right or left side (in this embodiment, left side) ofengine 21 and gear transmission 122. A PTO casing 127 is attached via amotor generator casing 126 onto the other left or right side (in thisembodiment, right side) of transaxle casing 122 opposite to belttransmission casing 125 in the lateral direction of vehicle V5. PTOshaft 128 projects forward from PTO casing 125. Front transaxle 133includes a rearwardly projecting input shaft 132 that is drivinglyconnected to PTO shaft 128 via a propeller shaft 130 with universaljoints 129 and 131. Front transaxle 133 incorporates a differential unit(not shown) differentially connecting right and left axles 134. Thisdifferential unit transmits the rotary power of input shaft 132 inputtedfrom PTO shaft 128 to right and left axles 134.

Referring to FIGS. 12 to 15, an interior structure of transaxle casing122 will be described. As shown in FIG. 12, transaxle casing 122includes left and right divisional casing parts 122 a and 122 b joinedto each other via a vertical joint plane. Laterally horizontal gearshafts 137, 142 and 148 and right and left coaxial axles 23 are extendedparallel to each other in transaxle casing 122. A right or left end (inthis embodiment, left end) of gear input shaft 137 projects fromtransaxle casing 122 and into belt transmission casing 125 (not shown inFIG. 12) so as to serve as a pulley shaft of a driven pulley 136. Inbelt transmission casing 125, driven pulley 136 is drivingly connectedto a drive pulley (not shown) configured on an engine output shaft ofengine 21, whereby the drive pulley, driven pulley 136 and belt 135constitute a belt transmission BT3.

As shown in FIGS. 13, 14 and 15, a spline collar 137 a is provided intransaxle casing 122. Spline collar 137 a has a hole that is splined onan inner peripheral surface thereof, and an axial end portion of gearinput shaft 137 opposite to belt transmission casing 125 isspline-fitted into this hole of spline collar 137 a. Spline collar 137 ais also splined on an outer peripheral surface thereof so that a parkingshifter 166 can be spline-fitted on the splined outer peripheral surfaceof spline collar 137 a. A governor weight 141 a of a centrifugalgovernor 141 is provided on an outer peripheral portion of spline collar137 a.

As shown in FIGS. 13, 14 and 15, in transaxle casing 122, a fixtureshaft 137 b is extended coaxially to gear input shaft 137 laterallyopposite to belt transmission casing 125. An axial projection is formedon one axial end of fixture shaft 137 b and is inserted into splinecollar 137 a via a bearing. Therefore, spline collar 137 a is fitted atone axial end thereof on gear input shaft 137 rotatably integrally withgear input shaft 137, and is fitted at the other axial end thereof onfixture shaft 137 b rotatably relative to fixture shaft 137 b. Fixtureshaft 137 b projects at the other axial end thereof outward fromtransaxle casing 122 via a hole of transaxle casing 122. A flange isformed on this axial end of fixture shaft 137 b disposed outside oftransaxle casing 122 laterally opposite to belt transmission casing 125and is fastened to transaxle casing 122 (right divisional casing part122 b) via bolts.

As shown in FIGS. 13, 14 and 15, in transaxle casing 122, a parkingshifter 166 is spline-fitted on an outer peripheral surface of fixtureshaft 137 b so that parking shifter 166 is axially slidable on fixtureshaft 137 b and is unrotatable relative to fixture shaft 137 b, i.e.,the rotational position of parking shifter 166 is fixed to transaxlecasing 122 via fixture shaft 137 b. Due to the axial slide of parkingshifter 166, it is selected whether or not parking shifter 166 isspline-fitted on the splined outer peripheral surface of spline collar137 a.

As shown in FIG. 12, a reverse drive gear 138, a low-speed drive gear139 and a high-speed drive gear 140 are fixed or formed on gear inputshaft 137. A reverse driven gear 144 and a high-speed driven gear 146are fitted on first counter shaft 142 so as to be rotatable relative tofirst counter shaft 142. A low-speed driven gear 145 is fitted on acentral boss portion of high-speed driven gear 146 so as to be rotatablerelative to high-speed driven gear 146. Reverse drive gear 138 andreverse driven gear 144 mesh with each other via an idle gear (notshown) so that gears 138 and 144 and the idle gear constitute a backwardtraveling gear train RG3. Low-speed drive gear 139 and low-speed drivengear 145 directly mesh with each other so as to constitute a low-speedforward traveling gear train LFG. High-speed drive gear 140 andhigh-speed driven gear 146 directly mesh with each other so as toconstitute a high-speed forward traveling gear train HFG.

A shifter 143 is spline-fitted on an axial intermediate portion of firstcounter shaft 142 between a central boss portion of backward travelingdriven gear 144 and the central boss portion of high-speed forwardtraveling driven gear 146 so as to be unrotatable relative to firstcounter shaft 142 and so as to be axially slidable on first countershaft 142. FIG. 12 shows shifter 143 set at a neutral position whereshifter 143 meshes with none of driven gears 144, 145 and 146. Shifter143 is able to slide in one direction (leftward in FIG. 12) from theneutral position so as to be set at a backward traveling position whereshifter 143 meshes with the central boss portion of reverse driven gear144. Shifter 143 is able to slide in the other direction (rightward inFIG. 12) from the neutral position so as to be set at a high-speedforward traveling position (a normal forward traveling position) whereshifter 143 meshes with the central boss portion of high-speed drivengear 146. Shifter 143 is able to slide further in the other direction(further rightward in FIG. 12) from the high-speed forward travelingposition so as to be set at a low-speed forward traveling position (aworking forward traveling position) where shifter 143 meshes withlow-speed driven gear 145. In other words, when shifter 143 is set atone of the backward traveling position, the low-speed forward travelingposition and the high-speed forward traveling position, shifter 143fixes corresponding driven gear 144, 145 or 146 to first counter shaft142 so as to transmit the rotary power of gear input shaft 137 to firstcounter shaft 143 via the corresponding one of gear trains RG3, HFG andLFG

A gear 147 is fixed on first counter shaft 142, a gear 149 is fixed onsecond counter shaft 148, and gears 147 and 149 mesh with each other soas to transmit power from first counter shaft 142 to second countershaft 148. A gear 155 is fixed or formed on second counter shaft 148. Adifferential gear unit D1 is disposed in transaxle casing 122 so as todifferentially connect right and left axles 23 to each other. Gear 155meshes with a differential input gear (bull gear) 156 of differentialgear unit D1 so as to transmit power from second counter shaft 148 todifferential gear unit D1.

Differential gear unit D1 is similar to differential unit D in transaxlecasing 22 of engine-transmission assembly 20 shown in FIG. 3, exceptthat differential input gear 156 has a central boss fitted on one(right) axle 23, a differential casing 157 is fixed to differentialinput gear 156 and has a central boss fitted on the other (left) axle23, and a differential lock clutch 158 is spline-fitted on the one(right) axle 23 so as to be able to mesh with the central boss ofdifferential input gear 156. The fitting of the central bosses ofdifferential input gear 156 and differential casing 157 onto respectiveaxles 23 transmits rotation of differential input gear 156 anddifferential casing 157 to axles 23, however, allows differentialrotation of right and left axles 23 as far as differential lock clutch158 is set at a differential unlock position to disengage from thecentral boss of differential input gear 156. When differential lockclutch 158 is set at a differential lock position to mesh with thecentral boss of differential input gear 156, differential input gear 156and differential casing 157 are locked to (right) axle 23 on whichdifferential lock clutch 158 is spline-fitted, thereby locking right andleft axles 23 to each other. Incidentally, for convenience ofunderstanding, an upper part of differential lock clutch 158 above axle23 in FIG. 12 is drawn as being located at the differential lockposition and a lower part of differential lock clutch 158 below axle 23in FIG. 12 is drawn as being located at the differential unlockposition.

Referring to FIG. 12, interior structures of motor generator casing 126and PTO casing 127 will be described. Motor generator casing 126 isfixed to one (right) side portion of transaxle casing 122 laterallyopposite to belt transmission casing 125 so as to avoid interfering withbelt transmission casing 125. A rotor shaft 160 is journalled in motorgenerator casing 126 and is extended coaxially to second counter shaft148 in transaxle casing 122. One axial end portion of rotor shaft 160projects from motor generator casing 126 into transaxle casing 122 andis connected (spline-fitted) to second counter shaft 148 so as to berotatably integral with second counter shaft 148.

PTO casing 127 is fixed on one (right) side of motor generator casing126 laterally opposite to transaxle casing 122. The other axial endportion of rotor shaft 160 projects from motor generator casing 126 intoPTO casing 127 and is fixedly provided thereon with a bevel gear 164.PTO shaft 128 is journalled in PTO casing 127 and is fixedly provided onan end portion thereof with a bevel gear 165. Bevel gears 164 and 165mesh with each other so as to transmit power from second counter shaft148 to PTO shaft 128 via rotor shaft 160.

In motor generator casing 126, a rotor 163 having a magnet is fixed onrotor shaft 160. A stator 162 having an armature is fixed on an innerperipheral surface of motor generator casing 126 and is disposed tosurround rotor 163. In this way, stator 162 and rotor 163 constitutemotor generator 161. When electric power is supplied from a battery (notshown) to the armature of stator 163, motor generator 161 functions asan electric motor so as to drive rotor shaft 160. This driving of rotorshaft 160 by the motor function of motor generator 161 drives axles 23and PTO shaft 128 without power of engine 21 or assists second countershaft 148 driven by power of engine 21 via belt transmission BT3 todrive axles 23 and PTO shaft 128. When electric power is not supplied tothe armature of stator 162 and engine 21 outputs power to drive axles 23and PTO shaft 128, rotor shaft 160 and rotor 161 rotate together withsecond counter shaft 148 so as to make the armature of stator 162generate an electricity, whereby motor generator 161 functions as agenerator.

When motor generator 161 functions as the generator, motor generator 161also functions as a regenerative brake. In this regard,engine-transmission assembly 120 has belt transmission BT3 that is acontinuously variable transmission (CVT) lacking the function of enginebraking. The regenerative braking function of motor generator 161compensates for the lack of engine braking function. Therefore,engine-transmission assembly 120, even having the CVT, is advantageousin having an effective brake comparable to an engine brake of anordinary car having a gearshift transmission.

Incidentally, any one of shafts 137, 142 and 148 in transaxle casing 122may be used to be joined to rotor shaft 160 if it is available totransmit power to PTO shaft 128 and to ensure the configuration of motorgenerator 161 in motor generator casing 126 attached to transaxle casing122.

Operation of parking shifter 166 and governor weight 141 a disposed intransaxle casing 122 as mentioned above will now be described withreference to FIGS. 13, 14 and 15. Parking shifter 166 is operativelyconnected to a parking shift arm 167 via a fork 166 a. Parking shift arm167 is operatively connected to a parking manipulator (not shown)provided in vehicle V5. Parking shifter 166 is shiftable between aparking-on position shown in FIG. 13 and a parking-off position shown inFIG. 14 according to manipulation of the parking manipulator. Parkingshifter 166 set at the parking-on position is extended and spline-fittedonto the outer peripheral surface of spline collar 137 a so as to lockgear input shaft 137 and spline collar 137 a to fixture shaft 137 b.Parking shifter 166 set at the parking-off position is not extended ontothe outer peripheral surface of spline collar 137 a, thereby allowinggear input shaft 137 and spline collar 137 a to rotate relative tofixture shaft 137 b.

During the setting of parking shifter 166 at the parking-off position,as the rotary speed of gear input shaft 137 increases by driving engine21, governor weight 141 a of centrifugal governor 141 rotates andfinally contacts an axial end of parking shifter 166 at the parking-offposition as shown in FIG. 15, thereby preventing parking shifter 166from unexpectedly moving toward the parking-on position, and therebypreventing gear input shaft 137 from being unexpectedly locked tofixture shaft 137 b (i.e., to transaxle casing 122) during traveling ofvehicle V5.

Incidentally, a sensor 168 shown in FIGS. 13, 14 and 15 detects whetheror not parking shifter 166 or fork 166 a is disposed at the parking-onposition. A warning light is lighted on an indicator or an alarm issounded in vehicle V5 according to a detection signal from sensor 168.

Similarly, transaxle casing 122 is provided therein with sensors (notshown) for detecting a position of shifter 143, more strictly, fordetecting a position of a fork 169 fitted on shifter 143. Fork 169 ismounted on a fork shaft (not shown) disposed in transaxle casing 122parallel to first counter shaft 142 so as to be axially slidablyintegral with the fork shaft 170, thereby enabling shifter 143 toaxially slide on first counter shaft 142 along with the axial movementof the fork shaft. One of the sensors detects an axial slide position ofthe fork corresponding to the backward traveling position of shifter143, and another of the sensors detects another axial slide position ofthe fork corresponding to the neutral position of shifter 143, therebyalarming an operator of real arrival of shifter 143 at the backwardtraveling position or the neutral position. A detailed description ofthese sensors of engine-transmission assembly 120 in structure and inpurpose relies on description of sensors 281 and 282 as shown in FIGS.19 and 20, which are provided in a later-discussed engine-transmissionassembly 220 for the same purpose.

FIG. 16 shows a four-wheel drive vehicle V6 equipped with an alternativeengine-transmission assembly 220 including a continuously variable belttransmission (CVT) BT4 and a motor generator 251. Thisengine-transmission assembly 220 also has the advantage in that motorgenerator 251 functions as the regenerative brake compensating for thelack of engine brake function of belt transmission BT4. In vehicle V6,central engine-transmission assembly 220 distributes output powerbetween a front transaxle 260 carrying front wheels 14 and a reartransaxle 270 carrying rear wheels 24. In this regard,engine-transmission assembly 220 has an output shaft 245 projectingforward and rearward at front and rear ends thereof. The front end ofoutput shaft 245 is drivingly connected to an input shaft 262 of fronttransaxle 260 via a propeller shaft 255 with a universal joint or/andthe like. The rear end of output shaft 245 is drivingly connected to aninput shaft 272 of rear transaxle 270 via a propeller shaft 256 with auniversal joint or/and the like.

A differential unit 263 is disposed in a transaxle casing 261 of fronttransaxle 260, and a differential unit 273 is disposed in a transaxlecasing 271 of rear transaxle 270. In this embodiment, rear wheeldifferential unit 273 is drawn as an ordinary differential gearmechanism, and front wheel differential unit 263 is drawn as abi-directive clutch. These are only examples. Each differential unit mayhave any structure. Further, rear differential unit 273 is provided witha differential locking mechanism 273 a, which may be provided as needed.

Front wheel differential unit 263 is drivingly connected to axles 14 aof right and left front wheels 14 via respective propeller shafts 263with universal joints. Alternatively, differential unit 263 maydifferentially connect axles 14 a of right and left front wheels 14without propeller shafts 265 having universal joints. On the other hand,rear wheel differential unit 273 differentially connects axles 23 ofright and left rear wheels 24 to each other. Alternatively, propellershafts with universal joints such as propeller shafts 265 may beinterposed between respective differential yoke shafts of differentialunit 273 and respective axles 23. Right and left brakes 274 are providedon respective right and left axles 23 in transaxle casing 271.Alternatively, a brake for braking output shaft 245 may be provided inengine-transmission assembly 220.

Referring to FIG. 17, engine-transmission assembly 220 will be describedon an assumption that engine-transmission assembly 220 is arranged tohave belt transmission BT4 forward of engine 21. Engine-transmissionassembly 220 is a combination of engine 21 and a transmission assembly,and this transmission assembly includes a transmission casing 222.Transmission casing 222 includes a front housing 222 a, a middle housing222 b and a rear housing 222 c. An open front end of middle housing 222b is joined to an open rear end of front housing 222 a, and an open rearend of middle housing 222 b is joined to an open front end of rearhousing 222 c, thereby constituting transmission casing 222. A partitionwall is formed in middle housing 222 b between the open front and rearends of middle housing 222 b so as to divide an inner space of middlehousing 222 b into front and rear spaces. An inner space in fronthousing 222 a and the front space in middle housing 222 b joined tofront housing 222 a are defined as a belt transmission chamber C1forward of the partition wall. An inner space in rear housing 222 c andthe rear space in middle housing 222 b joined to rear housing 222 c aredefined as a gear transmission chamber C2 rearward of the partitionwall.

Middle housing 222 b is extended to have a vertical face, and a frontend of engine 21 is fixed to this vertical face of middle housing 222 bso that engine 21 and gear transmission chamber C2 are juxtaposed in adirection perpendicular to the fore-and-aft direction ofengine-transmission assembly 220, e.g., upper and lower or right andleft. Horizontal engine output shaft 26 of engine 21 projects forwardinto belt transmission chamber C1 via the vertical face of middlehousing 222 b so as to serve as a drive pulley shaft 26 having a drivepulley 227 thereon. A driven pulley shaft 230 is journalled by thepartition wall of middle housing 222 b via a bearing. Driven pulleyshaft 230 is extended forward from the partition wall into belttransmission chamber C1 so as to have a driven pulley 229 thereon. Abelt 228 is looped over pulleys 227 and 229 in belt transmission chamber228. Whereby engine-transmission assembly 220 includes belt transmissionBT4 having belt transmission chamber C1 incorporating belt 228 andpulleys 227 and 229.

Drive pulley 230 extends rearward from the partition wall of middlehousing 222 b into gear transmission chamber C2 so as to serve as aninput shaft 230 of a gear transmission configured in gear transmissionchamber C2. This gear transmission includes shafts 230, 234, 236, 242and 245 and gears on these shafts. The partition wall in middle housing222 b journals the intermediate portion of input shaft 230 via thebearing as mentioned above. Further, the partition wall in middlehousing 222 b supports a front end of shaft 234, journals front ends ofshafts 236 and 242 via respective bearings and journals an intermediateportion of shaft 245 via a bearing. A partition wall is formed in rearhousing 222 c to define a rear end of gear transmission chamber C2. Thepartition wall in rear housing 222 c supports a rear end of shaft 234,journals rear ends of shafts 230 and 242 via respective bearings andjournals intermediate portions of shafts 236 and 245 via respectivebearings.

A high speed drive gear 231, a low speed drive gear 232 and a reversedrive gear 233 are fixed or formed on input shaft 230 so as to berotatably integral with shaft 230. A high speed driven gear 237 isfitted at a central boss thereof on first counter shaft 236 so as to berotatable relative to first counter shaft 236. Gears 231 and 237directly mesh with each other so as to constitute a high speed geartrain HG2. The central boss of high speed driven gear 237 is axiallyextended along first counter shaft 236 so as to have a low speed drivengear 238 fitted thereon so that low speed driven gear 238 is rotatablerelative to high speed driven gear 237. Gears 232 and 238 directly meshwith each other so as to constitute a low speed gear train LG2. Areverse driven gear 239 is fitted on first counter shaft 236 so as to berotatable relative to counter shaft 236. An idling gear 235 is fitted onidling gear shaft 234 and directly meshes with gears 233 and 239. Gears233, 235 and 239 constitute a reverse gear train RG4.

A shifter 240 is spline-fitted on first counter shaft 236 between thecentral boss of high speed driven gear 237 and a central boss of reversedriven gear 239 so as to be not rotatable relative to shaft 236 and soas to be axially slidable along shaft 236. A fork 241 is fitted onshifter 240. FIG. 17 shows a low speed forward traveling position L, ahigh speed forward traveling position H, a neutral position N and abackward traveling position R as positions of fork 241. When fork 241 isdisposed at low speed forward traveling position L, shifter 240 mesheswith low speed driven gear 238 so as to drivingly connect first countershaft 236 to input shaft 230 via low speed gear train LG2. When fork 241is disposed at high speed forward traveling position H, shifter 240meshes with the central boss of high speed driven gear 237 so as todrivingly connect first counter shaft 236 to input shaft 230 via highspeed gear train HG2. When fork 241 is disposed at neutral position N,shifter 240 meshes with none of gears 237, 238 and 239 so as to isolatefirst counter shaft 236 from a rotary force of input shaft 230. Whenfork 241 is disposed at backward traveling position R, shifter 240meshes with the central boss of reverse driven gear 239 so as todrivingly connect first counter shaft 236 to input shaft 230 via reversegear train RG4.

Counter gears 243 and 244 are fixed on second counter shaft 242. Countergear 243 directly meshes with a gear 239 fixed on first counter shaft236. Counter gear 244 directly meshes with a gear 246 fixed on outputshaft 245. Whereby gears 239, 243, 244 and 246 transmit power from firstcounter shaft 236 to output shaft 245 via second counter shaft 242.Output shaft 245 extends forward from the partition wall in middlehousing 222 b into belt transmission chamber C1. Output shaft 245 isextended through a space in belt transmission chamber C1 between aportion of belt 228 running from pulley 227 to pulley 229 and a portionof belt 228 running from pulley 229 to pulley 227. A front end portionof output shaft 245 projects forwardly outward from a front surface offront housing 222 a so as to be drivingly connected to front transaxleFT (see FIG. 18). A rear end portion of output shaft 245 projectsrearwardly outward from a rear portion of rear housing 222 c definingthe partition wall in rear housing 222 c so as to be drivingly connectedto rear transaxle RT (see FIG. 18).

The rear portion of rear housing 222 c is partly expanded rearward so asto be formed as a flange to which a front end of a motor generatorcasing 223 is fastened via a spacer 223 a. The flange of rear housing222 c and spacer 223 a fixed to the flange of rear housing 222 c definesa shaft connection chamber C3 therein. A rear end portion of firstcounter shaft 236 projects rearward from the partition wall in rearhousing 222 c into shaft connection chamber C3. Motor generator casing223 and spacer 223 a journal a rotor shaft 248 via respective bearings.A front end portion of rotor shaft 248 projects forward from motorgenerator casing 223 into shaft connection chamber C3 via spacer 223 acoaxially to first counter shaft 236. In shaft connection chamber C3, acoupling sleeve 247 is spline-fitted on the rear end portion of firstcounter shaft 236 and the front end portion of rotor shaft 248 so as todrivingly integrate rotor shaft 248 with first counter shaft 236.

Motor generator casing 223 and spacer 223 a define a motor generatorchamber C4 therein. In motor generator chamber C4, a stator 250 witharmature windings is fixed to an inner peripheral surface of motorgenerator casing 223 so as to surround a magnet rotor 249 fixed on rotorshaft 248. Whereby an electric motor generator 251 including rotor 249and stator 250 is configured in motor generator casing 223.

On an assumption that engine 21 is driven and fork 241 is set at anyposition other than neutral position N, rotor shaft 248 follows rotationof first counter shaft 236 so that motor generator 251 functions as agenerator when motor generator 251 is not supplied with electric powerfrom a battery. Motor generator 251 functioning as the generator alsofunctions as a regeneration brake serving as an engine brake of avehicle having a multi-speed transmission.

On the same assumption, motor generator 251 functions as an electricmotor for assisting engine 21 to drive output shaft 245 when motorgenerator 251 is supplied with electric power from the battery. Ifengine 21 is not driven or fork 241 is set at neutral position N, motorgenerator 251 when it is supplied with electric power functions as theelectric motor to drive output shaft 245 without power of engine 21.Motor generator 251 functioning as the electric motor serves as acontinuously variable transmission for steplessly changing the speed ofoutput shaft 245.

Motor generator casing 223 incorporating motor generator 251 includingrotor shaft 248 can be easily handled so as to be optionally attached toa predetermined portion of transmission casing 222, thereby enabling toselect whether or not engine-transmission assembly 220 is provided withmotor generator 251. Alternatively, a design of engine-transmissionassembly 220 may be changed so as to have rotor shaft 248 of motorgenerator 251 connected to any shaft in gear transmission chamber C2,e.g., input shaft 230 or second counter shaft 242, other than firstcounter shaft 236.

Referring to FIGS. 18, 19 and 20, an arrangement of shifters 281 and 282for detecting a position of shifter 240 (more specifically, fork 241) isshown. In transmission casing 222, a fork shaft 280 having fork 241fitted thereon is extended parallel to first counter shaft 236, as shownin FIGS. 18 and 19. Fork shaft 280 is axially slidable and is formed onan axial end portion thereof with detent grooves 280 a corresponding tothe low-speed forward traveling position, high-speed forward travelingposition, neutral position and backward traveling position of fork 241.

Sensors 281 and 282 are fitted into transmission casing 222 (morespecifically, rear housing 222 c) as shown in FIGS. 19 and 20. Annularprojections 241 a and 241 b are formed on an outer peripheral surface ofa cylindrical portion of fork 241 fitted on fork shaft 280. Sensor 281responds to projection 241 a when fork 241 reaches the neutral position,thereby detecting a real arrival of shifter 240 at the neutral position.Sensor 282 responds to projection 241 b when fork 241 reaches thebackward traveling position, thereby detecting a real arrival of shifter240 at the backward traveling position. Alternatively, another sensorfor detecting fork 241 arriving at the high speed forward travelingposition or the low speed forward traveling position.

The movement of shifter 240 directly responds to the axial movement offork 241 and fork shaft 280. On the other hand, the axial movement offork shaft 280 depends on an operation of a solenoid valve according todetection of a position of a gearshift manipulator in vehicle V5.Accordingly, there is a time lag between the position of the gearshiftmanipulator recognized by an operator and the actual position of shifter240. It is difficult for the operator to recognize this time lag.Therefore, when sensor 281 or 282 detects the position of fork 241corresponding to the actual position of shifter 240, the actual arrivalof shifter 240 at the backward traveling position or the neutralposition is indicated on an indicator in vehicle V5, thereby preventingsuch a wrong condition that, although the gearshift manipulator has beenshifted to the neutral position, the vehicle does not desirably reduceits traveling speed or stop because shifter 240 does not reach theneutral position, or such a wrong condition that, although the gearshiftmanipulator has been shifted to the backward traveling position, thevehicle does not desirably start traveling backward because shifter 240does not reach the backward traveling position.

It is further understood by those skilled in the art that the foregoingdescription is a preferred embodiment of the disclosed apparatus andthat various changes and modifications may be made in the inventionwithout departing from the scope thereof defined by the followingclaims.

What is claimed is:
 1. A hybrid utility vehicle comprising: a pair offront wheels; a front differential gear unit for differentiallyconnecting the front wheels; a pair of rear wheels; a rear differentialgear unit for differentially connecting the rear wheels; an internalcombustion engine configured as a power source of at least the rearwheels; an electric motor configured as a power source of at least thefront wheels; a body frame comprising a front side support portion forsupporting the front wheels, a rear side support portion for supportingthe rear wheels, and an arrangement portion comprising a driver's seatdisposed between the front side support portion and the rear sidesupport portion; and a boarding floor positioned in front of thearrangement portion of the driver's seat on the body frame; wherein theinternal combustion engine and the electric motor are disposed rearwardof the boarding floor.
 2. The hybrid utility vehicle according to claim1, wherein the front wheels and the rear wheels are configured to bedriven by switching between a state in which the internal combustionengine is used as a common power source and a state in which theelectric motor is used as a common power source.
 3. A hybrid utilityvehicle comprising: a pair of front wheels; a front differential gearunit for differentially connecting the front wheels; a pair of rearwheels; a rear differential gear unit for differentially connecting therear wheels; an internal combustion engine configured as a common powersource for the front wheels and the rear wheels; an electric motorconfigured as a common power source for the front wheels and the rearwheels; a body frame comprising a front side support portion forsupporting the front wheels, a rear side support portion for supportingthe rear wheels, an arrangement portion comprising a driver's seatdisposed between the front side support portion and the rear sidesupport portion; and a boarding floor positioned in front of thearrangement portion of the driver's seat on the body frame; wherein theinternal combustion engine and the electric motor are disposed rearwardof the boarding floor.
 4. The hybrid utility vehicle according to claim3, wherein the internal combustion engine and the electric motor areconfigured such that when the front wheels and the rear wheels aredriven by the internal combustion engine, the electric motor is drivenby the internal combustion engine, and such that when the front wheelsand the rear wheels are driven by the electric motor, a transmission ofpower between the electric motor and the internal combustion engine isdisconnected.